70 



COMPARATIVE MORPHOLOGY OF FUNGI 



Leptomitaceae. — In the structure of their thallus, this family probably 

 forms a considerably modified series parallel to the Saprolegnieae, and 

 to the uniflagellate Blastocladiaceae. All species so far known are aquatic. 



One of the simpler species is Leptomitus lacteus, saprophytic in sewage 

 rich in nitrogen. It covers everything with a dirty white, slimy coat, 

 and in luxuriant development the mycelial masses become loosened in 

 clumps, move away and collect in quiet spots where their mass and rapid 

 decomposition cause trouble. The mycelium is ramose, the main axes 

 are at times better developed. As in Gonapodya of the Blastocladiaceae 

 (Fig. 35, 1), the main axis and branches are generally divided into seg- 

 ments by constrictions. Each segment contains one or more granules 



Fig. 41.- — Rhipidium europaeum. 1. Plant with zoosporangia. 2. Zoosporangium during 



exit of spores. (After Minden, 1916.) 



of cellulin, a carbohydrate probably closely allied to cellulose: it is still 

 unknown whether these granules serve as reserve materials or as plugs, 

 because if they reach a stricture, they swell and fuse with the membrane 

 so that a septum-like valve is formed. In this manner, a septation of 

 the mycelium may be simulated. The sporangia correspond to segments 

 and are sometimes formed in short chains. The zoospores are ovoid and, 

 as in Pythiopsis of the Saprolegniaceae, possess two apical flagella. They 

 often escape through a lateral pore. Sexual organs have not yet been 

 found; under unfavorable conditions, however, gemmae are formed. 



The species of Apodachlya as A. pyrifera, on rotting plant substrates, 

 agree in habit with Leptomitus, and like Achlya can renew sporangia by 

 lateral sprouting. In the germination of their sporangia they are also 



